III group nitride compound semiconductor luminescent element

ABSTRACT

A Group III nitride compound semiconductor light-emitting device includes a multilayer having a quantum well structure containing an InGaN well layer and an AlGaN barrier layer. The film thickness, growth rate and growth temperature of the InGaN layer as the well layer and the film thickness of the AlGaN layer as the barrier layer are controlled to be optimized to thereby improve an output of the light-emitting device.

TECHNICAL FIELD

The present invention relates to a Group III nitride compoundsemiconductor light-emitting device. Particularly, it relates to a GroupIII nitride compound semiconductor light-emitting device for emittinglight at a relatively short wavelength.

BACKGROUND ART

A Group III nitride compound semiconductor light-emitting device isknown as a light-emitting diode for emitting light in a color rangingfrom blue to green. The Group III nitride compound semiconductorlight-emitting device is also used as a light-emitting diode foremitting light at a shorter wavelength (in a range of fromnear-ultraviolet to ultraviolet) than the wavelength of visible light.

Although the Group III nitride compound semiconductor light-emittingdevice emitting light at such a short wavelength is heretofore known,higher light-emitting efficiency and output have been required of thelight-emitting device recently.

DISCLOSURE OF THE INVENTION

The present inventors have made eager examination to improve the GroupIII nitride compound semiconductor light-emitting device emitting lightat a short wavelength. As a result, a light-emitting device having thefollowing configuration has been conceived. That is, there is provided aGroup III nitride compound semiconductor light-emitting deviceincluding: a multilayer containing a quantum well structure having anInGaN well layer and an AlGaN barrier layer; and an intermediate layerof InGaN thicker than the InGaN well layer and disposed below themultilayer.

According to the Group III nitride compound semiconductor light-emittingdevice configured as described above, light at a short wavelength, e.g.,a wavelength of 360–550 nm can be emitted with a high output comparedwith the conventional device.

Moreover, a multilayer containing a quantum well structure having anInGaN well layer and an AlGaN barrier layer is employed, and the filmthickness, growth rate and growth temperature of each of the InGaNlayers as the well layers and the film thickness of each of the AlGaNlayers as the barrier layers are controlled to be optimized.Accordingly, the output of the Group III nitride compound semiconductorlight-emitting device is improved.

In addition, the intermediate layer which serves as an undercoat layerfor the multilayer is also optimized. Also from this point of view,improvement in output of the Group III nitride compound semiconductorlight-emitting device is attained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the relation between the film thickness of each InGaN layeras a well layer and the light-emitting intensity of a light-emittingdevice;

FIG. 2 shows the relation between the growth rate of each InGaN welllayer and the light-emitting intensity of the light-emitting device;

FIG. 3 shows the relation between the growth temperature of each InGaNwell layer and the light-emitting intensity of the light-emittingdevice;

FIG. 4 shows the relation between the film thickness of each AlGaN layeras a barrier layer and the light-emitting intensity of thelight-emitting device;

FIG. 5 shows the relation between the growth temperature of a firstintermediate layer of InGaN and the light-emitting intensity of thelight-emitting device;

FIG. 6 shows Group III nitride compound semiconductor layers in alight-emitting device according to an embodiment of the invention;

FIG. 7 shows a configuration of the light-emitting device according tothis embodiment of the invention;

FIG. 8 shows Group III nitride compound semiconductor layers in alight-emitting device according to another embodiment;

FIG. 9 shows Group III nitride compound semiconductor layers in alight-emitting device according to a further embodiment;

FIG. 10 shows the relation between the film thickness of each InGaNlayer as a well layer and the light-emitting intensity of alight-emitting device;

FIG. 11 shows the relation between the growth rate of each InGaN welllayer and the light-emitting intensity of the light-emitting device; and

FIG. 12 shows the relation between the film thickness of each AlGaNlayer as a barrier layer and the light-emitting intensity of thelight-emitting device.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below in detail.

According to an aspect of the invention, the wavelength range aiming atimproving the light-emitting output is 360–550 nm but the wavelengthrange is not particularly limited. The wavelength range aiming atimproving the light-emitting output in the invention is more preferably360–520 nm, more and more preferably 360–490 nm, more and more and morepreferably 360–460 nm, most preferably 360–430 nm.

In this description, each Group III nitride compound semiconductor isrepresented by the general formula Al_(X)Ga_(Y)In_(1-X-Y)N (0≦X≦1,0≦Y≦1, 0≦X+Y≦1) which includes so-called binary compounds such as AlN,GaN and InN, and so-called ternary compounds such as Al_(X)Ga_(1-X)N,Al_(X)In_(1-X)N and Ga_(X)In_(1-X)N (0<x<1 in the above). The group IIIelements may be at least partially replaced by boron (B), thallium (Tl),or the like. The nitrogen (N) may be at least partially replaced byphosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), or the like.Each Group III nitride compound semiconductor layer may contain anoptional dopant. Si, Ge, Se, Te, C, or the like, can be used as n-typeimpurities. Mg, Zn, Be, Ca, Sr, Ba, or the like, can be used as p-typeimpurities. Incidentally, after doped with p-type impurities, the GroupIII nitride compound semiconductor may be subjected to electron beamirradiation, plasma irradiation or heating due to a furnace but thisprocess is not essential. A method for forming the Group III nitridecompound semiconductor layer is not particularly limited. Besides ametal organic chemical vapor deposition method (MOCVD method), the GroupIII nitride compound semiconductor layer can be formed by a known methodsuch as a molecular beam epitaxy method (MBE method), a halide vaporphase epitaxy method (HVPE method), a sputtering method, an ion-platingmethod, an electron showering method, or the like.

In this invention, specific Group III nitride compound semiconductorsare used for forming specific layers respectively.

In the invention, the multilayer contains an InGaN well layer and anAlGaN barrier layer which is a light-emitting layer. The multilayer hasa laminated structure in which each of the InGaN well layers issandwiched between AlGaN layers.

In another aspect, the multilayer is configured so that a unit pair madeof a laminate of an AlGaN layer and an InGaN well layer is laminated ortwo or more unit pairs are laminated, and an AlGaN layer or a GaN layeris finally laminated. That is, the p-type layer side uppermost layer isan AlGaN layer or a GaN layer. On the other hand, the intermediate layerside lowermost layer is also an AlGaN layer or a GaN layer. Acombination of the uppermost layer of AlGaN and the lowermost layer ofAlGaN, a combination of the uppermost layer of AlGaN and the lowermostlayer of GaN or a combination of the uppermost layer of GaN and thelowermost layer of GaN is preferable.

The number of unit pairs is selected to be preferably 1–10, morepreferably 2–8, more and more preferably 3–7, more and more and morepreferably 3–6, most preferably 3.5.

The wavelength of emitted light entirely depends on the compositionalratio of In and Ga in the InGaN well layer.

In order to emit short-wavelength light, the compositional ratio of Inis selected to be preferably 1–20%, more preferably 1–15%, more and morepreferably 1–10%, most preferably 1–8%.

FIG. 1 shows the relation between the film thickness of each InGaN layeras a well layer and the light-emitting intensity of the light-emittingdevice at 20 mA (hereinafter, the light-emitting intensity of thelight-emitting device expresses light-emitting intensity at the time ofapplication of 20 mA if no special notice is given). A result of FIG. 1is obtained when the thickness of each of InGaN well layers forming themultilayer is changed as shown in the horizontal axis in thelight-emitting device 1 shown in Embodiments (see FIGS. 6 and 7).

It is obvious from the result of FIG. 1 that the film thickness of eachInGaN well layer is selected to be preferably 90–200 Å (9.0–20.0 nm),more preferably 100–175 Å (10.0–17.5 nm).

FIG. 2 shows the relation between the growth rate of each InGaN welllayer and the light-emitting intensity of the light-emitting device.

A result of FIG. 2 is obtained when the growth rate of each of InGaNwell layers forming the multilayer is changed as shown in the horizontalaxis in the light-emitting device shown in Embodiments.

It is obvious from the result of FIG. 2 that the growth rate of eachInGaN well layer is selected to be preferably 0.25–0.35 Å/s (0.025–0.035nm/s).

For obtaining the result of FIG. 2, the flow rate of material gas (TMG,TMI, ammonia) is changed to control the growth rate.

FIG. 3 shows the relation between the growth temperature of each InGaNwell layer and the light-emitting intensity of the light-emittingdevice.

A result of FIG. 3 is obtained when the growth temperature of each ofInGaN well layers forming the multilayer is changed as shown in thehorizontal axis in the light-emitting device shown in Embodiments.

From the result of FIG. 3, the growth temperature of each InGaN welllayer is selected to be preferably 770–790° C., more preferably 777–783°C.

FIG. 4 shows the relation between the film thickness of each AlGaN layeras a barrier layer and the light-emitting intensity of thelight-emitting device. A result of FIG. 4 is obtained when the thicknessof each AlGaN layer is changed as shown in the horizontal axis in thelight-emitting device shown in Embodiments.

It is obvious from the result of FIG. 4 that the film thickness of eachAlGaN layer is selected to be preferably 50–125 Å (5.0–12.5 nm).

Incidentally, the uppermost layer in the multilayer is preferably formedto be thicker by 10–30% than any other barrier layers because theuppermost layer serves as a cap layer.

In a further aspect of the invention, attention is paid to anintermediate layer under the multilayer. The intermediate layer isobtained by laminating a first intermediate layer of InGaN, a secondintermediate layer of GaN and a third intermediate layer of AlGaNsuccessively. Preferably, each of the first, second and thirdintermediate layers is not doped. The third intermediate layer of AlGaNmay be omitted. If the second intermediate layer of GaN is omitted, thethird intermediate layer of AlGaN becomes the second intermediate layer.The second intermediate layer may be also regarded as a laminate of aGaN layer and an AlGaN layer.

FIG. 5 shows the relation between the growth temperature of the firstintermediate layer of InGaN and the light-emitting intensity of thelight-emitting device.

A result of FIG. 5 is obtained when the growth temperature of the firstintermediate layer of InGaN is changed as shown in the horizontal axisin the light-emitting device shown in Embodiments.

From the result of FIG. 5, the growth temperature of the firstintermediate layer of InGaN is selected to be preferably 770–875° C.,more preferably 800–850° C.

According to the inventors' more examination, it has been found that apreferred light-emitting output is obtained also when the InGaN welllayers and the AlGaN barrier layers are provided in the followingconditions. That is, in the conditions shown in FIGS. 10, 11 and 12, apreferred light-emitting output is obtained particularly at a wavelengthof 360–430 nm.

A result of FIG. 10 is obtained when the thickness of each of InGaN welllayers forming the multilayer is changed as shown in the horizontal axisin the light-emitting device 1 shown in Embodiments (see FIGS. 6 and 7).It is obvious from the result of FIG. 10 that the film thickness of eachInGaN well layer is selected to be preferably 20–60 Å (2.0–6.0 nm), morepreferably 35–50 Å (3.5–5.0 nm).

A result of FIG. 11 is obtained when the growth rate of each of InGaNwell layers forming the multilayer is changed as shown in the horizontalaxis in the light-emitting device shown in Embodiments. It is obviousfrom the result of FIG. 11 that the growth rate of each InGaN well layeris selected to be preferably 0.08–0.18 Å/s (0.008–0.018 nm/s). Forobtaining the result of FIG. 11, the flow rate of material gas (TMG,TMI, ammonia) is changed to control the growth rate.

A result of FIG. 12 is obtained when the thickness of each of AlGaNlayers is changed as shown in the horizontal axis in the light-emittingdevice shown in Embodiments. It is obvious from the result of FIG. 12that the film thickness of each AlGaN layer is selected to be preferably75–135 Å (7.5–13.5 nm). In an aspect of the invention, each barrierlayer is preferably formed to be thicker than each well layer.

EMBODIMENTS

Embodiments of the invention will be described below.

First Embodiment

FIG. 6 shows a semiconductor laminated structure of a light-emittingdiode 1 according to this embodiment.

Specifications of respective layers are as follows.

Layer Composition:Dopant (Thickness) Second p-type layer 17p-Al_(0.02)Ga_(0.98)N:Mg (75 nm) First p-type layer 16p-Al_(0.10–0.45)Ga_(0.90−0.55)N:Mg (smaller than 70 nm) Multilayer 15Uppermost layer 15d Al_(0.04–0.10)Ga_(0.96−0.90)N (5–10.5 nm) Barrierlayer 15c Al_(0.04–0.10)Ga_(0.96−0.90)N (5–10.5 nm) Well layer 15bIn_(0.01–0.07)Ga_(0.99−0.93)N (3.5–5 nm) Lowermost layer 15aAl_(0.04–0.10)Ga_(0.96−0.90)N (5–10.5 nm) Third intermediateAl_(0.10–0.45)Ga_(0.90−0.55)N (10 nm) layer 14c Second intermediate GaN(10 nm) layer 14b First intermediate In_(0.01–0.10)Ga_(0.99−0.90)N (200nm) layer 14a n-type later 13 n-GaN:Si (4 μm) Buffer layer 12 AlN (20nm) Substrate 11 sapphire (face a) (350 μm)

Incidentally, carrier concentration is as follows.

The carrier concentration in the second p-type layer 17 is not lowerthan 1×10¹⁷/cm³.

The carrier concentration in the first p-type layer 16 is0.5–2.0×10¹⁷/cm³.

The intermediate layers 14 a to 14 c are substantially not doped.

The carrier concentration in the n-type layer 13 is not lower than1.0×10¹⁸/cm³.

The substrate temperature (growth temperature) of the n-type layer 13,the first p-type layer 16 and the second p-type layer 17 is selected tobe not lower than 1000° C. Although a so-called low-temperature bufferlayer can be used as the buffer layer, a high-temperature buffer layeris employed in this embodiment (see Unexamined Japanese PatentPublication No. 2001-015443).

The light-emitting diode configured as described above is produced asfollows.

First, while hydrogen gas is circulated into a reactor of an MOCVDapparatus, the sapphire substrate 11 is heated to 1130° C. so that asurface (face a) is cleaned.

Then, at the substrate temperature, TMA and NH₃ are introduced and thebuffer layer 12 of AlN is grown by an MOCVD method.

Then, in the condition that the substrate temperature is kept at 1130°C., the n-type layer 13 is formed and Group III nitride compoundsemiconductor layers 14 to 17 following the n-type layer 13 are formedaccording to an ordinary method (MOCVD method).

In the MOCVD method, an ammonia gas and gases of Group III element alkylcompounds such as trimethylgallium (TMG), trimethylaluminum (TMA) andtrimethylindium (TMI) are supplied onto the substrate heated to anappropriate temperature and are subjected to a heat decompositionreaction to thereby grow a desired crystal on the substrate. Silane ordisilane is used for introducing silicon (Si) as impurities. (RC₅H₄)₂Mgis used for introducing magnesium (Mg) as impurities.

As described above, the substrate temperature for growing the firstintermediate 14 a is preferably selected to be 770–875° C. (see FIG. 5).In this embodiment, the substrate temperature is selected to be 800° C.

The substrate temperature for growing each InGaN well layer 15 b in themultilayer 15 is preferably selected to be 770–790° C. as shown in FIG.3. In this embodiment, the substrate temperature is selected to be 780°C.

The growth temperature of the AlGaN layer 15 a in the multilayer 15 isnot particularly limited if the well layer containing indium (In) is noteliminated at this temperature. In this embodiment, the substratetemperature is selected to be 885° C.

The substrate temperature of the first p-type layer 16 and the secondp-type layer 17 is kept at 1000° C.

Then, while Ti/Ni is used as a mask, the semiconductor layers arepartially removed by reactive ion etching to thereby reveal the n-typelayer 13 on which an n-electrode pad 21 will be formed (see FIG. 7).

A photo resist is applied on a semiconductor surface uniformly. Thephoto resist is removed from an electrode-forming portion on the secondp-type layer 17 by photolithography to thereby reveal the portion of thesecond p-type layer 17. An Au—Co translucent electrode layer 19 isformed on the revealed second p-type layer 17 by an evaporationapparatus.

Then, a p-electrode pad 20 and an n-electrode pad 21 are vapor-depositedin the same manner as described above.

Short-wavelength light having a peak wavelength of 382 nm is emittedefficiently from the light-emitting diode configured as described above.

Second Embodiment

This embodiment is configured in the same manner as in the firstembodiment except that the lowermost layer 15 a′ of the multilayer 15 inthe device according to the first embodiment is made of GaN as shown inFIG. 8.

Also in this embodiment, short-wavelength light having a peak wavelengthof 382 nm is emitted efficiently.

Third Embodiment

This embodiment is configured in the same manner as in the firstembodiment except that the lowermost layer 15 a′ of the multilayer 15 inthe device according to the first embodiment is made of GaN and theupper most layer 15 d′ thereof is made of GaN as shown in FIG. 9.

Also in this embodiment, short-wavelength light having a peak wavelengthof 382 nm is emitted efficiently.

Fourth Embodiment

The semiconductor configuration of a light-emitting diode according tothis embodiment is the same as shown in FIG. 6. Specifications ofrespective layers are as follows.

Layer Composition:Dopant (Thickness) Second p-type layer 17p-Al_(0.02)Ga_(0.98)N:Mg (75 nm) First p-type layer 16p-Al_(0.10–0.45)Ga_(0.90−0.55)N:Mg (smaller than 70 nm) Multilayer 15Uppermost layer 15d Al_(0.04–0.20)Ga_(0.96−0.80)N (5–18.0 nm) Barrierlayer 15c Al_(0.04–0.20)Ga_(0.96−0.80)N (5–13.5 nm) Well layer 15bIn_(0.01–0.20)Ga_(0.99−0.80)N (2–6 nm) Lowermost layer 15aAl_(0.04–0.20)Ga_(0.96−0.80)N (5–13.5 nm) Third intermediateAl_(0.10–0.45)Ga_(0.90−0.55)N (10 nm) layer 14c Second intermediate GaN(10 nm) layer 14b First intermediate In_(0.01–0.10)Ga_(0.99−0.90)N (200nm) layer 14a n-type later 13 n-GaN:Si (4 μm) Buffer layer 12 AlN (20nm) Substrate 11 sapphire (face a) (350 μm)

Incidentally, carrier concentration is as follows.

The carrier concentration in the second p-type layer 17 is not lowerthan 5×10¹⁶/cm³.

The carrier concentration in the first p-type layer 16 is0.5–2.0×10¹⁷/cm³.

The intermediate layers 14 a to 14 c are substantially not doped.

The carrier concentration in the n-type layer 13 is not lower than1.0×10¹⁸/cm³.

INDUSTRIAL APPLICABILITY

The invention is not limited to the description of the mode for carryingout the invention and the embodiments thereof at all, but includesvarious modifications that can be conceived easily by those skilled inthe art, without departing from the scope of claim for a patent.

This application is based on Japanese Patent Application (PatentApplication No. 2001-128507) filed on Apr. 25, 2001 and Japanese PatentApplication (Patent Application No. 2001-167589) filed on Jun. 4, 2001,the entirety of which is incorporated herein by reference.

The following items are disclosed below.

-   1. A Group III nitride compound semiconductor light-emitting device    for emitting light at a wavelength of 360–550 nm, including: a    multilayer containing a quantum well structure having an InGaN well    layer and an AlGaN barrier layer; and an intermediate layer of InGaN    thicker than the InGaN well layer and disposed below the multilayer,    wherein the Group III nitride compound semiconductor light-emitting    device satisfies at least one of the following requirements (2) to    (5):    -   (2) the film thickness of the InGaN well layer is 9.0–20.0 nm;    -   (3) the growth rate of the InGaN well layer is 0.025–0.035 nm/s;    -   (4) the growth temperature of the InGaN well layer is 770–790°        C.; and    -   (5) the film thickness of the AlGaN layer is 5.0–12.5 nm.-   2. A Group III nitride compound semiconductor light-emitting device    according to the item 1, wherein the InGaN well layer is thicker    than the AlGaN layer.-   2-1. A Group III nitride compound semiconductor light-emitting    device according to the item 1 or 2, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of GaN.-   2-2. A Group III nitride compound semiconductor light-emitting    device according to the item 1 or 2, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of GaN and AlGaN.-   2-3. A Group III nitride compound semiconductor light-emitting    device according to the item 1 or 2, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of AlGaN.-   3. A Group III nitride compound semiconductor light-emitting device    according to the item 1 or 2, wherein an intermediate layer obtained    by laminating a first intermediate layer of InGaN, a second    intermediate layer of GaN and a third intermediate layer of AlGaN    successively is formed under the multilayer.-   4. A Group III nitride compound semiconductor light-emitting device    according to the item 3, wherein the intermediate layer    substantially contains no impurities.-   5. A Group III nitride compound semiconductor light-emitting device    according to the item 3 or 4, wherein: the lowermost layer of the    multilayer being in contact with the third intermediate layer is    made of AlGaN or GaN; and the uppermost layer of the multilayer    being in contact with a p-type layer is made of AlGaN or GaN.-   6. A Group III nitride compound semiconductor light-emitting device    according to the item 5, wherein: the lowermost layer is made of    AlGaN; and the uppermost layer is made of AlGaN.-   7. A Group III nitride compound semiconductor light-emitting device    according to the item 5, wherein: the lowermost layer is made of    GaN; and the uppermost layer is made of GaN.-   8. A Group III nitride compound semiconductor light-emitting device    according to the item 5, wherein: the lowermost layer is made of    GaN; and the uppermost layer is made of AlGaN.-   9. A Group III nitride compound semiconductor light-emitting device    according to any one of the items 3 through 8, wherein the growth    temperature of the first intermediate layer of InGaN is 770–875° C.-   11. A method of producing a Group III nitride compound semiconductor    light-emitting device having a multilayer having a quantum well    structure having an InGaN well layer and AlGaN barrier layers as    layers for emitting light at a wavelength of 360–550 nm, the method    of producing a Group III nitride compound semiconductor    light-emitting device executing at least any one of the following    requirements (3) and (4):    -   (3) the growth rate of the InGaN well layer is 0.025–0.035 nm/s;        and    -   (4) the growth temperature of each of the InGaN well layer is        770–790° C.-   12. A method of producing a Group III nitride compound semiconductor    light-emitting device according to the item 11, wherein an    intermediate layer obtained by laminating a first intermediate layer    of InGaN, a second intermediate layer of GaN and a third    intermediate layer of AlGaN successively is formed under the    multilayer in the Group III nitride compound semiconductor    light-emitting device in the condition that the first intermediate    layer of InGaN is formed at a growth temperature of 770–875° C.-   21. A Group III nitride compound semiconductor light-emitting device    including: a multilayer containing a quantum well structure having    an InGaN well layer and AlGaN barrier layers; and an intermediate    layer of InGaN thicker than the InGaN well layer and disposed below    the multilayer, wherein the Group III nitride compound semiconductor    light-emitting device satisfies at least one of the following    requirements (2) to (5):    -   (2) the film thickness of the InGaN well layer is 9.0–20.0 nm;    -   (3) the growth rate of the InGaN well layer is 0.025–0.035 nm/s;    -   (4) the growth temperature of the InGaN well layer is 770–790°        C.; and    -   (5) the film thickness of the AlGaN layer is 5.0–12.5 nm.-   22. A Group III nitride compound semiconductor light-emitting device    according to the item 21, wherein the InGaN well layer is thicker    than the AlGaN layer.-   22-1. A Group III nitride compound semiconductor light-emitting    device according to the item 21 or 22, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of GaN.-   22-2. A Group III nitride compound semiconductor light-emitting    device according to the item 21 or 22, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of GaN and AlGaN.-   22-3. A Group III nitride compound semiconductor light-emitting    device according to the item 21 or 22, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of AlGaN.-   23. A Group III nitride compound semiconductor light-emitting device    according to the item 21 or 22, wherein an intermediate layer    obtained by laminating a first intermediate layer of InGaN, a second    intermediate layer of GaN and a third intermediate layer of AlGaN    successively is formed under the multilayer.-   24. A Group III nitride compound semiconductor light-emitting device    according to the item 23, wherein the intermediate layer    substantially contains no impurities.-   25. A Group III nitride compound semiconductor light-emitting device    according to the item 23 or 24, wherein: the lowermost layer of the    multilayer being in contact with the third intermediate layer is    made of AlGaN or GaN; and the uppermost layer of the multilayer    being in contact with a p-type layer is made of AlGaN or GaN.-   26. A Group III nitride compound semiconductor light-emitting device    according to the item 25, wherein: the lowermost layer is made of    AlGaN; and the uppermost layer is made of AlGaN.-   27. A Group III nitride compound semiconductor light-emitting device    according to the item 25, wherein: the lowermost layer is made of    GaN; and the uppermost layer is made of GaN.-   28. A Group III nitride compound semiconductor light-emitting device    according to the item 25, wherein: the lowermost layer is made of    GaN; and the uppermost layer is made of AlGaN.-   29. A Group III nitride compound semiconductor light-emitting device    according to any one of the items 23 through 28, wherein the growth    temperature of the first intermediate layer of InGaN is 770–875° C.-   31. A laminate including a quantum well structure having an InGaN    well layer and AlGaN barrier layers, wherein the laminate satisfies    at least one of the following requirements (2) to (5):    -   (2) the film thickness of the InGaN well layer is 9.0–20.0 nm;    -   (3) the growth rate of the InGaN well layer is 0.025–0.035 nm/s;    -   (4) the growth temperature of the InGaN well layer is 770–990°        C.; and    -   (5) the film thickness of the AlGaN layer is 5.0–12.5 nm.-   32. A laminate according to the item 31, wherein the InGaN well    layer is thicker than the AlGaN layer.-   32-1. A laminate according to the item 31 or 32, further including a    second intermediate layer formed between the quantum well structure    and the InGaN intermediate layer and made of GaN.-   32-2. A laminate according to the item 31 or 32, further including a    second intermediate layer formed between the quantum well structure    and the InGaN intermediate layer and made of GaN and AlGaN.-   32-3. A laminate according to the item 31 or 32, further including a    second intermediate layer formed between the quantum well structure    and the InGaN intermediate layer and made of AlGaN.-   33. A laminate according to the item 31 or 32, wherein an    intermediate layer obtained by laminating a first intermediate layer    of InGaN, a second intermediate layer of GaN and a third    intermediate layer of AlGaN successively is formed under the    multilayer.-   34. A laminate according to the item 33, wherein the intermediate    layer substantially contains no impurities.-   35. A laminate according to the item 33 or 34, wherein: the    lowermost layer of the multilayer being in contact with the third    intermediate layer is made of AlGaN or GaN; and the uppermost layer    of the multilayer being in contact with a p-type layer is made of    AlGaN or GaN.-   36. A laminate according to the item 35, wherein: the lowermost    layer is made of AlGaN; and the uppermost layer is made of AlGaN.-   37. A laminate according to the item 35, wherein: the lowermost    layer is made of GaN; and the uppermost layer is made of GaN.-   38. A laminate according to the item 35, wherein: the lowermost    layer is made of GaN; and the uppermost layer is made of AlGaN.-   39. A laminate according to any one of the items 33 through 38,    wherein the growth temperature of the first intermediate layer of    InGaN is 770–875° C.-   40. A laminate according to any one of the items 31 through 39,    wherein the multilayer contains light-emitting layers.-   41. A method of producing a Group III nitride compound semiconductor    light-emitting device having a multilayer containing a quantum well    structure having an InGaN-well layer and an AlGaN barrier layer, the    method of producing a Group III nitride compound semiconductor    light-emitting device executing at least any one of the following    requirements (3) and (4):    -   (3) the growth rate of the InGaN well layer is 0.025–0.035 nm/s;        and    -   (4) the growth temperature of the InGaN well layer is 770–790°        C.-   42. A method of producing a Group III nitride compound semiconductor    light-emitting device according to the item 41, wherein an    intermediate layer obtained by laminating a first intermediate layer    of InGaN, a second intermediate layer of GaN and a third    intermediate layer of AlGaN successively is formed under the    multilayer in the Group III nitride compound semiconductor    light-emitting device in the condition that the first intermediate    layer of InGaN is formed at a growth temperature of 770–875° C.-   51. A method of producing a laminate having a multilayer containing    a quantum well structure having an InGaN well layer and AlGaN    barrier layers, the method of producing a laminate executing at    least any one of the following requirements (3) and (4):    -   (3) the growth rate of the InGaN well layer is 0.025–0.035 nm/s;        and    -   (4) the growth temperature of the InGaN well layer is 770–7.90°        C.-   52. A method of producing a laminate according to the item 51,    wherein an intermediate layer obtained by laminating a first    intermediate layer of InGaN, a second intermediate layer of GaN and    a third intermediate layer of AlGaN successively is formed under the    multilayer in the condition that the first intermediate layer of    InGaN is formed at a growth temperature of 770–875° C.-   101. A Group III nitride compound semiconductor light-emitting    device for emitting light at a wavelength of 360–430 nm, including:    a multilayer containing a quantum well structure having an InGaN    well layer and an AlGaN barrier layer; and an intermediate layer of    InGaN thicker than the InGaN well layer and disposed below the    multilayer, wherein the Group III nitride compound semiconductor    light-emitting device satisfies at least one of the following    requirements (2) to (5):    -   (2) the film thickness of the InGaN well layer is 2.0–6.0 nm;    -   (3) the growth rate of the InGaN well layer is 0.008–0.018 nm/s;    -   (4) the growth temperature of the InGaN well layer is 770–790°        C.; and    -   (5) the film thickness of the AlGaN layer is 7.5–13.5 nm.-   102. A Group III nitride compound semiconductor light-emitting    device according to the item 101, wherein the AlGaN layer is thicker    than the InGaN well layer.-   102-1. A Group III nitride compound semiconductor light-emitting    device according to the item 101 or 102, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of GaN.-   102-2. A Group III nitride compound semiconductor light-emitting    device according to the item 101 or 102, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of GaN and AlGaN.-   102-3. A Group III nitride compound semiconductor light-emitting    device according to the item 101 or 102, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of AlGaN.-   103. A Group III nitride compound semiconductor light-emitting    device according to the item 101 or 102, wherein an intermediate    layer obtained by laminating a first intermediate layer of InGaN, a    second intermediate layer of GaN and a third intermediate layer of    AlGaN successively is formed under the multilayer.-   104. A Group III nitride compound semiconductor light-emitting    device according to the item 103, wherein the intermediate layer    substantially contains no impurities.-   105. A Group III nitride compound semiconductor light-emitting    device according to the item 103 or 104, wherein: the lowermost    layer of the multilayer being in contact with the third intermediate    layer is made of AlGaN or GaN; and the uppermost layer of the    multilayer being in contact with a p-type layer is made of AlGaN or    GaN.-   106. A Group III nitride compound semiconductor light-emitting    device according to the item 105, wherein: the lowermost layer is    made of AlGaN; and the uppermost layer is made of AlGaN.-   107. A Group III nitride compound semiconductor light-emitting    device according to the item 105, wherein: the lowermost layer is    made of GaN; and the uppermost layer is made of GaN.-   108. A Group III nitride compound semiconductor light-emitting    device according to the item 105, wherein: the lowermost layer is    made of GaN; and the uppermost layer is made of AlGaN.-   109. A Group III nitride compound semiconductor light-emitting    device according to any one of the items 103 through 108, wherein    the growth temperature of the first intermediate layer of InGaN is    770–875° C.-   111. A method of producing a Group III nitride compound    semiconductor light-emitting device having a multilayer having a    quantum well structure having an InGaN well layer and AlGaN barrier    layers as layers for emitting light at a wavelength of 360–430 nm,    the method of producing a Group III nitride compound semiconductor    light-emitting device executing at least any one of the following    requirements (3) and (4):    -   (3) the growth rate of the InGaN well layer is 0.008–0.018 nm/s;        and    -   (4) the growth temperature of the InGaN well layer is 770–790°        C.-   112. A method of producing a Group III nitride compound    semiconductor light-emitting device according to the item 111,    wherein an intermediate layer obtained by laminating a first    intermediate layer of InGaN, a second intermediate layer of GaN and    a third intermediate layer of AlGaN successively is formed under the    multilayer in the Group III nitride compound semiconductor    light-emitting device in the condition that the first intermediate    layer of InGaN is formed at a growth temperature of 770–875° C.-   121. A Group III nitride compound semiconductor light-emitting    device including: a multilayer containing a quantum well structure    having an InGaN well layer and AlGaN barrier layers; and an    intermediate layer of InGaN thicker than the InGaN well layer and    disposed below the multilayer, wherein the Group III nitride    compound semiconductor light-emitting device satisfies at least one    of the following requirements (2) to (5):    -   (2) the film thickness of the InGaN well layer is 2.0–6.0 nm;    -   (3) the growth rate of the InGaN well layer is 0.008–0.018 nm/s;    -   (4) the growth temperature of the InGaN well layer is 770–790°        C.; and    -   (5) the film thickness of the AlGaN layer is 7.5–13.5 nm.-   122. A Group III nitride compound semiconductor light-emitting    device according to the item 121, wherein the AlGaN layer is thicker    than the InGaN well layer.-   122-1. A Group III nitride compound semiconductor light-emitting    device according to the item 121 or 122, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of GaN.-   122-2. A Group III nitride compound semiconductor light-emitting    device according to the item 121 or 122, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of GaN and AlGaN.-   122-3. A Group III nitride compound semiconductor light-emitting    device according to the item 121 or 122, further including a second    intermediate layer formed between the quantum well structure and the    InGaN intermediate layer and made of AlGaN.-   123. A Group III nitride compound semiconductor light-emitting    device according to the item 121 or 122, wherein an intermediate    layer obtained by laminating a first intermediate layer of InGaN, a    second intermediate layer of GaN and a third intermediate layer of    AlGaN successively is formed under the multilayer.-   124. A Group III nitride compound semiconductor light-emitting    device according to the item 123, wherein the intermediate layer    substantially contains no impurities.-   125. A Group III nitride compound semiconductor light-emitting    device according to the item 123 or 124, wherein: the lowermost    layer of the multilayer being in contact with the third intermediate    layer is made of AlGaN or GaN; and the uppermost layer of the    multilayer being in contact with a p-type layer is made of AlGaN or    GaN.-   126. A Group III nitride compound semiconductor light-emitting    device according to the item 125, wherein: the lowermost layer is    made of AlGaN; and the uppermost layer is made of AlGaN.-   127. A Group III nitride compound semiconductor light-emitting    device according to the item 125, wherein: the lowermost layer is    made of GaN; and the uppermost layer is made of GaN.-   128. A Group III nitride compound semiconductor light-emitting    device according to the item 125, wherein: the lowermost layer is    made of GaN; and the uppermost layer is made of AlGaN.-   129. A Group III nitride compound semiconductor light-emitting    device according to any one of the items 123 through 128, wherein    the growth temperature of the first intermediate layer of InGaN is    770–875° C.-   131. A laminate including a quantum well structure having an InGaN    well layer and AlGaN barrier layers, wherein the laminate satisfies    at least one of the following requirements (2) to (5):    -   (2) the film thickness of the InGaN well layer is 2.0–6.0 nm;    -   (3) the growth rate of the InGaN well layer is 0.008–0.018 nm/s;    -   (4) the growth temperature of the InGaN well layer is 770–790°        C.; and    -   (5) the film thickness of the AlGaN layer is 7.5–13.5 nm.-   132. A laminate according to the item 131, wherein the AlGaN layer    is thicker than the InGaN well layer.-   132-1. A laminate according to the item 131 or 132, further    including a second intermediate layer formed between the quantum    well structure and the InGaN intermediate layer and made of GaN.-   132-2. A laminate according to the item 131 or 132, further    including a second intermediate layer formed between the quantum    well structure and the InGaN intermediate layer and made of GaN and    AlGaN.-   132-3. A laminate according to the item 131 or 132, further    including a second intermediate layer formed between the quantum    well structure and the InGaN intermediate layer and made of AlGaN.-   133. A laminate according to the item 131 or 132, wherein an    intermediate layer obtained by laminating a first intermediate layer    of InGaN, a second intermediate layer of GaN and a third    intermediate layer of AlGaN successively is formed under the    multilayer.-   134. A laminate according to the item 133, wherein the intermediate    layer substantially contains no impurities.-   135. A laminate according to the item 133 or 134, wherein: the    lowermost layer of the multilayer being in contact with the third    intermediate layer is made of AlGaN or GaN; and the uppermost layer    of the multilayer being in contact with a p-type layer is made of    AlGaN or GaN.-   136. A laminate according to the item 135, wherein: the lowermost    layer is made of AlGaN; and the uppermost layer is made of AlGaN.-   137. A laminate according to the item 135, wherein: the lowermost    layer is made of GaN; and the uppermost layer is made of GaN.-   138. A laminate according to the item 135, wherein: the lowermost    layer is made of GaN; and the uppermost layer is made of AlGaN.-   139. A laminate according to any one of the items 133 through 138,    wherein the growth temperature of the first intermediate layer of    InGaN is 770–875° C.-   140. A laminate according to any one of the items 131 through 139,    wherein the multilayer contains light-emitting layers.-   141. A method of producing a Group III nitride compound    semiconductor light-emitting device having a multilayer containing a    quantum well structure having an InGaN well layer and an AlGaN    barrier layer, the method of producing a Group III nitride compound    semiconductor light-emitting device executing at least any one of    the following requirements (3) and (4):    -   (3) the growth rate of the InGaN well layer is 0.008–0.018 nm/s;        and    -   (4) the growth temperature of the InGaN well layer is 770–790°        C.-   142. A method of producing a Group III nitride compound    semiconductor light-emitting device according to the item 141,    wherein an intermediate layer obtained by laminating a first    intermediate layer of InGaN, a second intermediate layer of GaN and    a third intermediate layer of AlGaN successively is formed under the    multilayer in the Group III nitride compound semiconductor    light-emitting device in the condition that the first intermediate    layer of InGaN is formed at a growth temperature of 770–875° C.-   151. A method of producing a laminate having a multilayer containing    a quantum well structure having an InGaN well layer and AlGaN    barrier layers, the method for producing a laminate executing at    least any one of the following requirements (3) and (4):    -   (3) the growth rate of the InGaN well layer is 0.008–0.018 nm/s;        and    -   (4) the growth temperature of the InGaN well layer is 770–790°        C.-   152. A method of producing a laminate according to the item 151,    wherein an intermediate layer obtained by laminating a first    intermediate layer of InGaN, a second intermediate layer of GaN and    a third intermediate layer of AlGaN successively is formed under the    multilayer in the condition that the first intermediate layer of    InGaN is formed at a growth temperature of 770° C.–875° C.

1. A Group III nitride compound semiconductor light-emitting devicecomprising: a multilayer having a quantum well structure containing anInGaN well layer and an AlGaN barrier layer; and an intermediate layerunder said multilayer, wherein said intermediate layer comprises: afirst intermediate layer of InGaN thicker than said InGaN well layer, asecond intermediate layer on said first intermediate layer, and a thirdintermediate layer of AlGaN on said second intermediate layer.
 2. TheGroup III nitride compound semiconductor light-emitting device accordingto claim 1, wherein said second intermediate layer comprises GAN.
 3. TheGroup III nitride compound semiconductor light-emitting device accordingto claim 1, wherein said second intermediate layer comprises AlGaN. 4.The Group III nitride compound semiconductor light-emitting deviceaccording to claim 1, wherein said second intermediate layer comprisesat least one of GaN and AlGaN.
 5. A Group III nitride compoundsemiconductor light-emitting device according to claim 1, wherein saidfirst intermediate layer substantially contains no impurities.
 6. AGroup III nitride compound semiconductor light-emitting device accordingto claim 2, wherein each of said first and second intermediate layerssubstantially contains no impurities.
 7. A Group III nitride compoundsemiconductor light-emitting device according to claim 3, wherein eachof said first and second intermediate layers substantially contains noimpurities.
 8. A Group III nitride compound semiconductor light-emittingdevice according to claim 4, wherein each of said first and secondintermediate layers substantially contains no impurities.
 9. A Group IIInitride compound semiconductor light-emitting device according to claim1, wherein each of said first, second and third intermediate layerssubstantially contains no impurities.
 10. The Group III nitride compoundsemiconductor light-emitting device according to claim 1, wherein: alowermost layer of said multilayer, being in contact with said thirdintermediate layer, comprises at least one of AlGaN and GaN; and anuppermost layer of said multilayer, being in contact with a p-typelayer, comprises at least one of AlGaN and GaN.
 11. A Group III nitridecompound semiconductor light-emitting device according to claim 1,wherein growth temperature of said first intermediate layer of InGaN is770–875° C.
 12. A method of producing the Group III nitride compoundsemiconductor light-emitting device of claim 1, the method comprising:forming said first intermediate layer of InGaN below said multilayer ina condition that said first intermediate layer of InGaN is formed at agrowth temperature of about 770 to about 875 degrees Celsius.
 13. Thedevice of claim 1, wherein said InGaN well layer has a thickness of fromabout 9.0 to about 20.0 nm.
 14. The device of claim 1, wherein saidAlGaN barrier layer has a thickness of from about 5.0 to about 12.5 nm.15. The device of claim 1, wherein said InGaN well layer has a thicknessof from about 2.0 to about 6.0 nm.
 16. The device of claim 1, whereinsaid AlGaN barrier layer has a thickness of from about 7.5 to about 13.5nm.
 17. The device of claim 1, wherein said AlGaN barrier layer isthicker than said InGaN well layer in said quantum well structure.
 18. AGroup III nitride compound semiconductor light-emitting devicecomprising: a multilayer having a quantum well structure; and anintermediate layer under said multilayer, wherein said intermediatelayer comprises: a first intermediate layer thicker than a well layer insaid quantum well structure, a second intermediate layer on said firstintermediate layer, and a third intermediate layer on said secondintermediate layer.
 19. The device of claim 18, wherein said thirdintermediate layer comprises AlGaN.
 20. The device of claim 18, whereinsaid first intermediate layer comprises InGaN and wherein said secondintermediate layer comprises at least one GaN, and AIGaN.